Fish live in water that much is obvious to us but do we realise how much the chemicals that form their water can impact upon them in both beneficial and negative ways?

Firstly the aquatic environment should be protected from all forms of manmade pollution and kept as close to the natural balance as possible. There is often a temptation to use chemicals to solve problems that have arisen in fish keeping. More often solving an issue with one chemical will introduce a new problem somewhere else; all water chemistry is connected. For example suddenly removing high levels of PO4 phosphate can reduce the waters buffering capacity which can cause PH crashes or make the PH change; this in turn can change NH4 to NH3 etc….

The best solution to correct issues in the aquarium water is to do water changes with good quality water and slowly correct the issue. When changing water it is always a good idea to try and keep key parameters as close as possible, a seneye device can be used to judge this. It is not just fish that are adversely affected by sudden change; many problems with filtration are caused by upsetting the bacteria through shocking them. If pollution is entering the aquarium from water change then it may be time to look at alternative sources of water or a water filter.

Fish are very adaptive so even though we often strive to reach ‘ideals’ fish can be happy in much more varied range of parameters than we imagine. What fish and all other aquatic organisms don’t like is change, as a rule if all looks well only make small changes over a long period!

The following parameters are the main ones we recommend watching to ensure the environment is stable.

Fast changing parameters that should be constantly monitored.

Water line as even though obvious aquariums can leak.

Temperature is often overlooked but the wrong temperature or sudden changes can cause damage to fish.

PH – the potential of hydrogen shows how acid or base your water is. Sudden changes can kill.

NH3 – ammonia gas is always present in aquariums where fish is present. There are a number of reasons why it can suddenly change and it is a deadly toxin. This is the number one killer of fish and very rarely directly measured.

These are slower changing but important parameters.

NO2 – nitrite, this is the second stage of the bacterial nitrification process for ammonia, it is toxic to fish but less toxic than ammonia.

NO3 – nitrate, this is the last stage of the aerobic nitrification process, if left unchecked levels will build until water changes take place. High levels will encourage algae growth.

Light – it doesn’t affect fish much but all plants and corals health is dictated by light quality and quantity.

These parameters might be useful to measure and know, especially if things aren’t going great.

GH – General Hardness. This is a measure of the calcium and magnesium in the water.

PO4 – Phosphate, High levels will encourage algae growth.

NH4 – ammonium, although not toxic itself a change in temperature or pH can release it into NH3.

There are many more exotic chemicals that can be measured in the aquatic environment but most of these will help organisms thrive the list above is designed to help them first survive.

WHAT IS PH?

pH is a measurement that shows the ratio of +/- hydrogen ions in concentration and is commonly used in the analysis of soil and water testing. The concept of pH was first introduced by Soren Sorensen in 1909 and revised to the modern pH scale in 1924 which is measured on a scale of 0 to 14 shown below.

In general terms pH of 7 is neutral, pH less than 7 is acidic, and pH greater than 7 is basic, therefore battery acid is more acidic than ammonia and baking soda is more basic than wine. The modern pH scale is logarithmic, which means that a unit decrease in pH is equal to a ten-fold increase in acidity e.g. rain (approx. pH 6) is at least ten times more acidic than distilled water (approx. pH 7).

Fish will live in a wide range of pH’s but are slow to adapt, most will live very happily at a wide range of pH’s. Sudden Change in pH can be very dangerous to Fish, plants, bacteria and other living creatures. A seneye device is an excellent way to get alerted to sudden change in the aquarium.

As a rule of thumb pH change in the aquarium should be minimised and anything above pH of 0.5 per day is counted as deadly or bad. Often aquarists changing water chemistry to reach absolute perfect values will cause more harm than good. If the fish are happy then a controlled and constant pH is most important. It is not uncommon to measure a big change when any pH device is recalibrated or new reagents are used; this does not mean the water has changed.

Daily swings in pH are common in the aquarium; the size of the swing is usually controlled by the hardness of the water (KH). This means marine systems will see very small swings as they have high buffer capacities (KH), however soft freshwater aquariums (especially Amazonian or black water tanks) will not normally have high KH and will react greater.

In the following passage we will try to explain how pH and KH are linked. As mentioned earlier the pH measurement is a ratio and how easy it is to change this ratio (pH stability) is dictated by the ionic (buffer) strength also known as KH. The images below illustrate how different ionic strengths can report the same pH value. If you imagine equal + hydrogen ions on one side of a balance to – hydrogen ions the other side then the level will flat or neutral. This would represent a pH of 7 and the absolute number of + or – ions on each side is not important so long as they balance.

If we were to mix the three different buffer strength waters shown above with and equal volume of water of a low pH (acidic) and weak buffer strength, say -5 ions & + 2 ions we can see the effect below.

As you can see the more highly buffered water doesn’t move much but the low buffered water moves huge amounts. Therefore the higher the buffering KH the more stable the pH. This is also why using RO water (which has no buffer strength) to lower pH will not work, it will however reduce the KH and pH stability.

A low KH will also make and pH changes hard as pH will usually revert back to where it was; the ability to resist pH change is often called alkalinity. Eventually a low KH will also often lead to pH crashes.

If you have a problem and do need to adjust pH up or down we recommend using both acid and base buffers; and always make changes over a long period.

In the fresh water aquarium is plants which use CO2 present in the water throughout the day during a process called photosynthesis. CO2 is a gas dissolved in the aquarium water and that makes it more acidic (like fizzy drinks), when plants have no light CO2 starts to build up and lower pH.